Hot pressure finishing apparatus for web materials



March l0, 1964 x-xoT PRESSURE FINIsHTNG APPARATUS EoR WEB MATERIALSFiled April 4, 1960 2 Sheets-Sheet 1 U om E MJ m P. J. i r .are

March 10, 1964 R. P. MAHONEY ETAL HOT PRESSURE FINISHING APPARATUS FORWEB MATERIALS Filed April 4. 1960 2 Sheets-Sheet 2 i fnf/E rifa/f'United States Patent O 3,124,450. HOT PRESSURE FINlSl-IENG APPARATUS FORWEB MATERIALS Ralph P. Mahoney and Edgar J. Justus, Beloit, Wis.,

'assigner-s, by mesne assignments, to Beloit Corporation, Beloit, Wis.,a corporation of Wisconsin Filed Apr. 4, 19st), Ser. No. 19,644

The present invention relates broadly to the production of paper yandrelated web materials and is more particularly concerned with improvedmethods and means for glossing paper and related web materials.

It is an object of the present invention to provide means for glossingcoated or uncoated paper and related web materials.

This and other objects, advantages and features of the present inventionwill become apparent upon a careful consideration of the followingdetailed description, when considered in conjunction with theaccompanying drawing illustrating preferred embodiments of the conceptsof our invention, wherein like reference characters and numerals referto like or corresponding parts throughout the several views.

On the drawings:

IFIGURE l is a partially diagrammatic view in side elevation ofapparatus for glossing one side of dried, coated paper constructed inaccordance with the concepts of our invention.

FIGURE 2 is a fragmentary view in side elevation illustrating the narrowwidth nip concept of the present invention shown on an enlarged scale.

FIGURE 3 is a partially diagrammatic View in side elevation illustratingapparatus for coating and glossing both sides of a ,coated paper Weib inaccordance with our invention.

FIGURE 4 is an enlarged fragmentary view in cross section illustratingthe influence of pressure and the hardness of the backing roll on webdeformation in the nip.

As shown on the drawing:

Briefly stated, the present invention involves glossing of eithercontinuous or discontinuous paper or related web materials by contactingthe surface with a polished finishing surface under temperatureconditions sufficient to cause or induce a temporary condition ofplasticity in the surface thereof and under pressure conditionssufficient to smooth, blend and polish the surface to thereby obtain ahigh degree of finish or gloss without crushing of the paper.

As appears in FIGURE 1, apparatus constructed in accordance with theprinciples of the present invention may be employed for glossing oneside of paper or related web materials.

`Uncoated paper or, if desired, previously coated paper Il may beconveyed over a plurality of guide rolls 12, 13, -14 and 15 to a feedroll 16 and thence in contact with a furnishing platen or backing rollL8 for the application of the particular coating employed. Pick up roll19 is utilized in the well `known manner and the web fed through the nipdefined by the furnishing roll 1-8 and the coating applicator roll 20.The web, freshly coated on one side, is then led around roll 21, and, inthis arrangement, the coating machine is of the air knife type having anair knife 22. It will be appreciated that the particular type of coatingmachine used will depend primarily upon the end product desired.

From the coating machine the coated web is next led over guide rolls 24and 25 for contact with a pair of conventional dryer rolls 26 and l27for drying of both sides of the coated web. The web is dried to acommercial or marketable moisture content (usually between ars/rasaPatented Mar. 10, i964 ICC and 10% bone dry) and the coating is,therefore, cornpletely plasticized or set when it leaves the dryer 27.

The web with its coating thus pre-dried and plasticized or set is nowready to be brought in contact with the highly polished finishing roll2S for the glossing treatment.

IIn the arrangement shown in FIGURE 1, the glossing apparatus may takethe form of a driven roll 28 having a highly polished finishing surfaceand a pair of hard surfaced but resilient backing rolls 29 and 3f).Backing rolls 29 and 30 may be driven by contact with the web 11 andfinishing roll 28 or drive means (not shown) may be provided.

The finishing rolls 28 may be constructed to provide the surfacetemperature required to plasticize the coating and coating surface ofthe paper web in the nip. For this purpose, a suitable source of heatmedium may be introduced into the chamber defined by the roll through aconduit 3l. The metal finishing roll 28 having a highly polished surfacedefines a narrow nip with the resiliently surfaced pressure backing roll29 of high surface hardness. The surface of the finishing roll 28 may beplated, as with chrome or nickel, and the resilient rolls 29 and 3G maycomprise a metal core having a rubber cover of the desired hardness.

For particular applications and in order to obtain a smooth levelsurface having excellent ink receptivity and printability, whileavoiding the high specular gloss comparable to that obtained by castcoating methods achieved with the chrome plated or highly polishedfinishing surtfaces, a smooth finished roll may be substituted for thehighly polished roll 28. We have also found that the web may beimmediately removed from the finishing nip without the necessity forpermitting extended contact between the web-and finishing roll andwithout damaging the gloss or other desirable characteristics of the weband coating.

In order to minimize the operating pressure loading of the respectiverolls, it is desirable that the resilient rolls 29 and Sil be `quitehard, i.e. less than 30 P. and J. GA3 ball). Employment of a hardsurfaced roll permits concentration of total uniform pressure loading ona relatively narrow nip, in the direction of travel of the web, and,excellent results have `been obtained when the nip is of across-sectional width, less than 1 and preferably about 1/2. Thedevelopment of high unit pressures in a narrow nip is desirable onlybelow the crushing point of the web fibers. The hard and narrow nipassures uniform loading across the entire width of the sheet. It will beappreciated of course, that continued use of the nip will tend to causethe resilient or hard rubber surfaced rolls 29 `and 30 to softenslightly due to the temperature conditions existing at the nip and dueto the effects of working engagement with the web during operation. Inorder to maintain the backing rolls at the desired high hardness leveland thereby the nip width within the desired limits, means may beemployed, if desired, to cool the resilient rolls. For this purpose, acooling -agent may be maintained in the interior of each of the backingrolls. As will be fully appreciated by those versed in the art this maybe done in various Ways and is shown schematically in FIGURE 1 bycoolant supply lines 29a and 30a leading to the rolls 29 and 30.

The temperatures maintained at the nip in conjunction with the other nipconditions, must be sufficient to induce momentarily or temporarily acondition of plasticity in the particular dried and set coating employedto permit the pressure applied by the backing roll to smooth, blend andgloss the thus plastic coating while in the nip. Generally thetemperature at the nip is maintained above the boiling point of water orother vehicle of the coating and no known upper temperature limits existother than the decomposition temperatures of the particular coatings andother materials involved. Thus any dried and set coating compositionwhich may be rendered plastic to the extent set forth in the abovedescribed manner may be employed in the present invention. Experiencehas indicated that the transversely and uniformly distributed highintensity unit pressure at the nip is preferably within the range fromabout 250 pounds per square inch to about 2400 pounds per square inch,depending primarily upon the particular coating and paper web involved.

Thus, in the nip, the pressure and the high surface temperature of thefinishing roll induce a condition of temporary plasticity in thepreviously pre-dried, plasticized or set coating, particularly in thesurface thereof, and impart a gloss finish to the plastic surface of thecoating, while at the same time the resilience of the hard surfacedbackiny roll permits suflicient yielding in the nip to minor webthickness inequalities whereby the bulk and opacity of the web is notmaterially reduced.

The above degree of resiliency avoids the disadvantages inherent inconventional calendering apparatuses and methods in which spot densityof the web is increased thereby producing hard glossy spots which willnot accept printing impressions. The unit pressures employed aresignificantly less than those employed in paper calendering machines andthe speeds obtainable are much higher than those normally available forcast coating applications.

Satisfactory gloss results are obtained at any practical operatingspeeds and therefore glossing operating speeds are limited only by theoperational speeds of the paper machine itself or the web supply meansand of the rolls. It will be appreciated that glossing temperatures aregenerally in direct relation to operating speeds. Por example,satisfactory glossing of coated board in the above manner which wassupplied at the rate of 500 feet per minute was obtained with finishingroll and nip temperatures of approximately 300 F. and nip pressures of400 lbs. per inear inch. Similarly, satisfactory glossing results wereobtained with a coated lightweight paper running at 2000 ft. per minutethrough a pressure nip of approximately 1A. inch width maintained at atemperature of 345 F. and pressures of 400 lbs. per linear inch.

The glossed, coated web may be immediately removed from the nip and fedto a winding reel, or may remain in contact with the iinishing roll forpurposes of positioning the coated web in the proper' manner preparatoryto a second glossing treatment. lt will be appreciated that the coatingis only momentarily r temporarily plastic While in the nip and that,upon leaving the nip, almost instantaneously returns to its previous setor plasticized condition without any deleterious effects on the coatingor web but with a gloss finish.

To vary the pressure applied at the nip for glossing of particularcoating surfaces, means therefor may take the form of a hydraulically orpneumatically operated piston assembly 33 having its piston rod 34connected to a cross arm 35 of a pair of support members 56 which carrybrackets 37 for mounting the shaft 38 of the backing roll 29. Thesupport members 35 may be pivotally mounted to the support stanchion 3%.Pneumatic or hydraulic operating pressures of the piston arrangementneed only be increased or decreased in order to produce a correspondingpressure on the finishing roll and web.

A similar piston arrangement may be employed for controlling applicationof glossing pressure by the resilient roll 30 which includes a pistonhousing (not shown), a piston rod i0 mounted on a cross arm of a pair ofsupport members di mounting the bearing brackets 42 for roll 30. Supportarms #il may be fulcrumed to a clevis 43 which is mounted on the framestanchion lid. Thus by employment of a pair of support members altransverse uniform pressure is applied at the nip.

r)Thus in operation the web having a set and dried coating thereon isintroduced into the hard, narrow width nip defined by rolls 23 and 29and the heat required at the nip plasticizes the coating or at least thesurface of the coating temporarily while inthe nip to a sufficientextent to permit the pressure exerted at the nip to smooth, blend andpolish the coating surface. Upon leaving the nip the coating immediatelysets and consequently may be removed to a winding reel. If desired, thecoated web may be left in contact with the finishing roll 28 for properintroduction thereof into the second glossing nip defined by rolls 2.3and 30. Alternately, the glossed coated web may be immediately removedfrom the nip and ledl around a pair of fly rolls 45 and 46, as appearsin FIGURE l, forsubsequent introduction to the nip defined by rolls 28'and 3d; Employment of fiy rolls 45 and do is made possible since thecoating is only temporarily plastic in the nip and upon removaltherefrom immediately sets without interruption or damage to either thecoating or web. lf desired, the now glossed and dry coated web may thenundergo a second polishing treatment in the nip defined by pressurebacking roll 30 and finishing roll 28. It will be appreciated that thepressure roll 30 is identical in construction and operation to roll 29.After leaving the latter nip, the web may be then fed over a guide roll47 to be wound on a reeler (not shown) awaiting subsequentlydisposition.

As appears in FIGURE 2 wherein the dried and set or hardened andimmobile coating layer of the web is shown'. in exaggerated form, thecoated web, in its set or hardened'and unglossed state, enter the narrowwidth and hard nip defined by rolls 28 and 29 with the hardened or setand dry coating brought in contact with the finishing surface of roll 2Swhere, while in the nip, the coating is momentarily or temporarilyrendered plastic and is blended, smoothed and polished in the nip. Itwill be appreciated that the desired glossing results are accomplishedwhere only one polishing nip is employed and that such apparatus may beutilized for on or off the paper making machine applications.

As appears in FIGURE 3, an alternative arrangement may be provided foron tor off the machine coating and glossing of bo-th sides of a paperweb. In this arrangement, the |web 11 is fed over a piluraldty of guiderolls 48, 49, 50' and 51 to a lfeed roll 52 for coating of one side ofthe web 'with the desired coating which may be applied by la trailingblade coating machine 53. The web is next carried over a fly roll 54 toa conventional dryer 55 where the contact of the non-coated surface ofthe web with the dryer dries the coating layer to an atmosphericmoisture content. As a result of contact with the heated surface of thedryer -roll lthe web coating is plasticized or set when i-t issubsequently introduced into the narrow width and hard glossing nipdefined by the heated finishing roll 55 and backing roll 57. It will beappreciated that rolls 56 land 57 are identical rin construction andopenation to rolls Z8 and Z9, respectively, of FIGURE 1. The web isintroduced into the nip with the coated surface in contact with thefinished sunface of rolll 56.

For glossing heavier web, such as board, it is preferable to bring thecoated surface of the web into contact with the finishing roll slightlyin advance of the nip, as shown, in order to pre-heat the coating webfor plasticizing of the coating in the nip.

The coated surface of the web in contact with the finishing surface ofroll 56 is temporarily or momentarily rendered plastic and glossed inthe nip. Upon leaving the nip the coated sur-falce of the webimmediately sets and, 'if desir-ed, may' be permitted to rerruain inContact with the finishing roll to be introduced into a second glossingnip defined lby finishing roll 56 and a second resi-lient backing roll58 which is -identical in 'construction and operation to backing roll57.

Means are provided for varying .the pressure `applied by rolls 57 and SSand may take the form of a hydraulically vor pneumatically operatedbellows arrangement 59.

The end cover 60 of the bellows arrangement may be connected to amovable 61 which is pivo-tally connected lat one end to an arm 62`ulcrummedto the bearing of the shaft 63 of roll 58. Arm 62 is connectedat the other end to a bracket 64 mounted on the frame stanchion V65.Similarly, the end plate 66 of the bellows arrangement may be connectedto a movable link 67 which is pivotally connected to a member 68rfulcrummed to the bearing of the shaft 69 of back-ing roll 57. Arm 60 ispivotally connected to a bracket '70 mounted on machine frame member`65. Similar, arm link and bracket assemblies, not shown, connect thebellows arrangement 59 to the opposite sides rolls 57 and 58 to obtainequal distribution of pressure transversely across the hard narrow widthnip. Thus, as pressure in the bellows .is increased, lthe bellows expandand rolls 57 and 5S will exert greater pressure against the finishingroll `56. Conversely, when pressure is decreased in the bellows, thebellows contract and less pressure is exerted by backing rolls 57 and 58yon finishing roll 56. It will be appreciated, however, tihat any`conventional means may be employed to vary pressure application byeither one or a pair of backing rolls depending upon the glrossingarrangement adopted.

Therefore, depending upon the particular rheology of the various coatingmaterials employed, simple and efective means may be provided to varythe pressure necessary to blend, smooth and polish the coating surfacein the Roller 58 is similar .in construction and operation to roller 57,land heated to- -a temperature suiiicient to render the particularcoating surface plastic in the nip is roll 56.

Alfter leaving the hard narrow width nip defined by rolls 56 and 58, theweb coating immediately returns to its set or plasticized condition andmay then be fed around the plurality of guide rolls 72 and 73 to a feedroll 74 for introduction thereof to la coating machine 75 for coating ofthe uncoated side of the web. After having been coated on the latterside, the web is then -fed over a fly roll 76 to a conventional dryer 77which may be similar `in construction and `operation to dryer Z6. Tlheweb -is fed to the dryer with the initially coated surface in contactwith the dryer. When the web leaves the dryer '77 it is `dried toatmospheric moisture content and the coating is completely plasticizedor set and immobile.

Upon leaving the dryer, the now dried and plasticized or set unglossedcoating of the paper is introduced into la hard, narrow width nip`defined by a highly polished finishing roll 7 S `and a resilientbacking roll having a surface of high hardness for gloss-ing of side ofthe paper web. An additional glossing treatment of the second side ofthe coated paper web may be accomplished, if desired, in a similar nip`defined by finishing roll '78` and a backing roll 79a. Finishing roll'78 may be similar in construction tand operation to finishing roll 56,and, similarly, backing rolls 79 and 79a may `be similar in constructionand operation to backing rolls 57 and 58 respectively. Means I80 similarin construction and operation to means l59 may be employed to vary thepressure applied by backing rolls 79' and 79a.

Thus when the web leaves the latter nip both sides of the coating areglossed, dried to atmospheric moisture content and plasticized or set.Giltossing of the second side rolf the coated web occurs withoutdisruption of the initially coated and lglossed surface or web.

The web with the glossed coating on both sides thereof mlay thentraverse a plurality of guide rolls 8l, 32, 83 and 84 and be taken offthe machine on a reeler (not shown) for subsequent disposition.

Experience has indicated that paper and board which had been printed byemployment of 'any of the several common printing methods could beprovided with a gloss finish, after printing, by' subjecting the printedpaper or board to a glossing process Iwhich employed apparatus:constructed in accordance with the principles of our in- Ventionwithout otherwise affecting the quality of the printing or othercharacteristics of the paper .or board. Lt is to be understood, ofcourse, that :for the above application the temperature and pressure atthe nip will depend to an extent upon the properties of the paper andprint undergoing treatment.

As an yadditional exemplification of our invention, a commercial gradeclay-casein paper coating composition applied dried and finished onpaper making apparatus as illustrated in FIG. l, and within thetemperature and pressure limits set forth above results in a coatingfinish `comparabile to commercial cast-surfaced coated paper nowconsidered acceptable in the trade. Satisfactory finishing results havebeen obtained for various coated paper :and related web materials withthe finishing surfaces heated to a ytemperature within the range of fromabout 220 F. to about 400 F., while we prefer to ernploy 'temperatureswithin the range of rorn about 280 F. to 360 F.

Thus by employment of `our invention we provide means for glossingdni-ed and plasticized or set coated paper and related coated webmaterials having a variety of applications.

In general, the heat and pressure in the hard, narrow nip should becontrolled to conform the surface being finished to the surface of thefinishing roll without crushing the web and under conditions whichaccommodate removal of the web without disturbing the conformed websurface. Usually, tolerable moisture contents are lessened withincreases in either nip temperature or nip pressure and enlarged withincreases in basic web weight.

FIGURE 4 presents a graphical illustration of the combined influence onpaper web material deformation of the pressure applied at the nip andthe resilient yielding characteristics of the hard backing roll. Undermicroscopic examination, the web W is of varying crosssectionalthickness, as shown exaggerated in FIGURE 4, consisting of surface peaksof higher density and valleys of lower density. 'Ihe valleys, of course,contain fibers and fibrils; however, the density of the web at thevalleys is less than the density of the web at the peaks.

Conventional calendering operations, wherein high pressures are appliedto the web, have an effect on web density and thickness which differsfrom the eliect of the nip conditions of the present invention whichpermits lower pressures to be applied to the web in the hard narrow nip.

The curve A in FIGURE 4 illustrates the characteristic deformation ofthe web caused by the high pressures applied when conventionalcalendering app-aratus is employed. The calendering pressures cause thegreatest deformation of' the web W at the peaks P and the leastdeformation of the web at the valleys V. The web W is shown in FIGURE 4as having peaks -and valleys ot equal `and sequential height and depthfor purposes of clarity only; however, it will be appreciated that thepeaks and Valleys are, in fact, of irregular heights ,and depths. Thedeformation of the web caused by the high pressures applied incalendering operations at the peaks result in the hard glossy spotsaforementioned which refuse to 'accept ink or print.

However, 'by employment of our invention, the other conditions at thenarrow nip, defined by the finishing roll 12 and the hard resilientlyyieldable backing roll 13, cooperate to permit employment of lowerpressures than those used in conventional calendering treat-ments andresult in lesser web deformation. In addition, the lesser webdeformation results in a more uniformly finished web surface.

As shown in curve B, the resilient backing roll 13 yields at the peaksP1 to an extent causing less web peak deformation and also less webvalley deformation than that caused by the conventional calenderingtreatments in the valleys V1 thus resulting in an overall smootherleveling of the web surface being finished. It will be appreciated,therefore, that the provision of a resiliently yieldable backing rollcooperating with the other nip conditions of the present inventionpermit uniform deformation and leveling of the web coated surface to adegree unattainable by employment of conventional calenderin gtreatments.

It is also apparent that the magnitude of the deformation of the backingroll is large only with regard to the thickness of the web beingfinished. Likewise the magnitude of `deformation of the backing roll issmall in the transverse .direction to insure maintenance of the hard,narrow nip l), at high unit pressure.

As used herein, the term dried is to be understood to mean coating driedsufficiently within the ranges herein specified so as not to adhere tothe non-resilient finishing surface while in the nip.

As used herein, the term polished refers t-o the treatment of thenon-resilient finishing surface to render the surface smooth, and thesurface may be mirror finished or polished to ya matte or like surface.

As used herein, the term plasticized is to be understood to mean thatthe web coating is hardened, immobile and rigid and the coated web is ina condition to be transported as an article of commerce without thenecessity of additional immobilizing treatments.

Although various minor modifications might be suggested by those versedin the art, it should be understood that we wish to embody within thescope of the patent warranted hereon all such embodiments as reasonablyand properly come within the scope of our contribution to the art.

We claim as our invention:

1. In an apparatus, for improving the surface characteristics of a paperweb, the combination comprising,

a first large diameter roll having a smooth precisely finishednon-resilient surface,

.a second roll formed of a metal core and an outer resilient coverhaving a high hardness being in nipdefining relationship with said firstroll,

said second rol-l being smaller than said first roll and forming anarrow nip therebetween,

a heating means for heating the surface of the first roll to plasticizethe surface of the web in the nip,

means forcing the rolls together forming a transversely uniformlydistributed high intensity unit pressure in said nip,

.and guide means separating the web from the surface of the first rollsubstantially immediately following the nip.

2. In an apparatus for improving the surface characteristics of a paperweb, they combination comprising,

a first large diameter roll having a smooth precisely finishednon-resilient surface,

a second roll formed of a metal core and an outer resilient cover havinga high hardness being in nipdefining relationship with said first roll,

said second roll being smaller than said first roll and forming a narrownip therebetween, heating means for heating the surface of the firstroll to plasticize the surface of the web in the nip,

y means for cooling said second roll for maintaining the cover of saidsecond roll at the desired high hardness,

and means forcing the rolls together forming a transversely uniformlydistributed high intensity unit of pressure in said nip.

3. In an apparatus for improving the surface characteristics of a paperweb, the combination comprising,

a first large diameter roll having a smooth precisely finishednon-resilient surface,

a second roll formed of a metal core and an outer resilient cover havinga high hardness being in nipdelining relationship with said first roll,

d said second roll being smaller than said first roll and forming anarrow nip therebetween,

heating means heating the surface of the first roll to a temperature ofbetween a lower limit of 220 F. and an upper limit up to thedecomposition point of the paper web to plasticize the surface of theweb in the and liiieans forcing the rolls together forming atransversely uniformly distributed high intensity unit pres- Sure insaid nip of between 250 pounds per squme inch to 2400 pounds per squareinch.

4. In an apparatus for improving the surface characteristics of a paperweb, the combination comprising,

a first large diameter roll having a smooth precisely finishednon-resilient surface,

a second roll formed of a metal core and a relitively thin outerresilient cover having a high hardness of less than 30 P. and i. (143ball) being in nip-defining relationship with said first roll,

said second roll being smaller than said first roll and forming a narrownip therebetween, heating means for heating the surface of the firstroll to a temperature of between a lower limit of 220 F. and an upperlimit up to the decomposition point of the web to plasticize the surfaceof the web in the nip,

and means forcing the rolls together forming a transversely uniformlydistributedv high intensity unit of pressure in said nip of between 25 0pounds per square inch to 2400 pounds per square inch.

5. In an apparatus for improving the surface characteristics of a paperweb, the combination comprising,

a first large diameter roll having a smooth precisely finishednon-resilient surface,

a second roll formed of a metal core and an outer resilient cover havinga high hardness being in nipdefining relationship with said first roll,

said second roll being smaller than said first roll and forming a narrowfirst nip therebetween, heating means for heating the surface of thefirst roil to a temperature of between a lower limit of 220 F. and anupper limit up to the decomposition point of the web to plasticize thesurface of the web in the nlp,

means forcing the rolls together forming a transversely uniformlydistributed high intensity unit of pressure in said nip,

a third roll formed of a metal core and a relatively thin outerresilient cover having a high hardness,

said third roll being smaller than said first roll and forming a narrowsecond nip therebetween located with respect to the first rollsubstantially diametrically opposite the first nip,

and means forcing the third and first rolls together forming atransversely uniformly distributed high intensity unit pressure in saidsecond nip with the web passing sequentially through said` first andsecond nip,

the pressures in said nips being between 250 pounds per square inch to2400 pounds per square inch.

6. In an apparatus for improvingl the surface characteristics of a paperweb, the combination comprising,

a first large diameter roll having a smooth precisely finishednon-resilient surface,

a second roli formed of a metal core and an outer resilient cover havinga high hardness being in nip-defining relationship with said first roll,

said second roll being smaller than said first roll and forming a narrownip therebetween,

heating means heating the surface of the first roll to a temperature ofbetween a lower limit of 220 F. and an upper limit up to thedecomposition point of the paper web to plasticize the surface of theweb in the mp,

a third large diameter roll having a smooth precisely finishednon-resilient surface,

a fourth roll formed of a metal core and an outer resilient cover havinga high hardness being in nip-defining relationship with said third roll,

said fourth roll being smaller than said third roll and forming a narrownip therebetween, heating means heating the surface of said third rollto a temperature of between a lower limit of 220 F. and an upper limitup to the decomposition point of the paper web to plasticize the surfaceof the web in the nip,

and means forcing said first and second rolls together and means forcingsaid third and fourth rolls together forming a transversely uniformlydistributed high intensity unit pressure in each of said nips of between250 pounds per square inch to 2400 pounds per square inch.

7. In an apparatus for imp-roving the surface characteristics of a paperweb, the combination comprising,

a first large diame-ter roll havin-g a smooth precisely finishednon-resilient surface,

a second roll .formed of a metal core and an outer resilient coverhaving a high hardness being in nipdefining relationship with said firstroll,

said second roll being smaller than said first roll and forming a narrownip therebetween, heating means for heating the surface of the lfirstroll to plasticize the surface of the web in the nip,

a third large diameter roll having a smooth precisely finishednon-resilient surface,

a fourth roll formed of a metal core and an outer resilient cover havinga high hardness being in nipdefining relationship with said third roll,

said fourth roll being smaller than said third roll and forming a narrownip therebetween,

heating means for heating the surface of the third roll to plasticizethe surface of the web in the nip,

means forcing said first and second rolls together and means forcingsaid third and fourth rol'ls together forming transversely uniformlydistributed high intensity unit pressures in said nips,

'guide means separating the vveb from the surface of the first rollsubstantially immediately following the nip between said first andsecond rolls,

and second guide means separating the web from the surface of the thirdroll substantially immediately following the nip between the third andfourth rol'ls.

8. lIn an apparatus for improving the surf-ace characteristics of apaper web, the combination comprising,

a coating mechanism applying liquid coating to the surface of the web,

means dry-ing the coating until -it is set,

a first large diameter roll having a smooth precisely finishednon-resilient surface,

a second roll formed of a metal core and an outer l resilient coverhaving a high hardness being in nipdefining relationship with said firstroll,

said second roll being smaller than said first roll and forming a narrownip therebetween,

heating rneans heating the surface of the first roll to a temperature ofbetween a lower limit of 220 F. and an upper limit up to thedecomposition point of the paper web to plasticize the surface of theweb in the nlp:

.and means forcing the rolls together forming a transversely uniformlydistributed high intensity unit presl sure in said nip of between 250pounds per square inch to 2400 pounds per square inch.

said web moving from the drying means into the nip between the rollswith a coated side engaging the surface of the first roll in the nip.

9. In an apparatus for improving the surface characteristics of a paperweb, the combination comprising,

a coating mechanism applying liquid coating to a surface of the web,

means drying the coating until it i-s set,

a first large diameter roll having a smooth precisely finishednon-resilient surface,

a second roll formed of a metal core and an outer resilient cover havinga high hardness being in nipdefining relationship with said first roll,

said second roll being smaller than said first roll and formi-ng anarrow nip therebetween, heating means for heating the surface of thefirst roll to plastieize the surface of the web in the nip, meansforcing the rolls together forming a transversely uniformly distributedhigh intensity lunit pressure in said nip,

and guide means separating the web from the surface of the first rollsubstantially immediately following the nip,

said web moving from the drying means into the nip between the rollswith `a coated side enga-ging the surface of the `rst roll in the nip.

10. In an `apparatus for improving the surface characteristics of apaper web, the combination comprising,

a coating mechanism applying liquid coating to a surface of the web,

means drying the coating until it is set,

a first large diameter roll havin-g a smooth precisely finishednon-resilient surface,

a second roll formed of a metal core and Ian outer resilient coverhaving a high hardness being in nipdefining relationship with saidlfirst roll,

said second roll being smaller than said first roll land forming anarrow nip therebetween,

heating means for heating the surface of the first roll to plasticizethe surface of the web in the nip,

means for cooling said second roll for maintaining the cover of saidsecond roll at the desired high hardness,

and means forcing the rolls together forming a transversely uniformlydistributed high intensity unit of pressure in said nip,

said web movin-g from the drying means into the nip between the rollswith a coated side engaging the surface of the first roll in the nip.

References Cited in the file of this patent UNITED STATES PATENTS OTHERREFERENCES Manufacture of Pulp and Paper (3rd ed), vol. V, McGraw-Hill(1939), New York (pages 1626 of section 3, a-nd pages 54-55 of section 4relied on).

Pulp & Paper Manufacture, vol. 3 (1953); McGraw- 70 Hill, New York(pages 275 and 675-679 relied on).

9. IN AN APPARATUS FOR IMPROVING THE SURFACE CHARACTERISTICS OF A PAPERWEB, THE COMBINATION COMPRISING, A COATING MECHANISM APPLYING LIQUIDCOATING TO A SURFACE OF THE WEB, MEANS DRYING THE COATING UNTIL IT ISSET, A FIRST LARGE DIAMETER ROLL HAVING A SMOOTH PRECISELY FINISHEDNON-RESILIENT SURFACE, A SECOND ROLL FORMED OF A METAL CORE AND AN OUTERRESILIENT COVER HAVING A HIGH HARDNESS BEING IN NIPDEFINING RELATIONSHIPWITH SAID FIRST ROLL, SAID SECOND ROLL BEING SMALLER THAN SAID FIRSTROLL AND FORMING A NARROW NIP THEREBETWEEN, HEATING MEANS FOR HEATINGTHE SURFACE OF THE FIRST ROLL TO PLASTICIZE THE SURFACE OF THE WEB INTHE NIP, MEANS FORCING THE ROLLS TOGETHER FORMING A TRANSVERSELYUNIFORMLY DISTRIBUTED HIGH INTENSITY UNIT PRESSURE IN SAID NIP, ANDGUIDE MEANS SEPARATING THE WEB FRM THE SURFACE OF THE FIRST ROLLSUBSTANTIALLY IMMEDIATELY FOLLOWING THE NIP, SAID WEB MOVING FROM THEDRYING MEANS INTO THE NIP BETWEEN THE ROLLS WITH A COATED SIDE ENGAGINGTHE SURFACE OF THE FIRST ROLL IN THE NIP.